Role of bismuth content on structural and luminescence properties of Ho3+ doped phosphate glasses

Abstract

0.5 mol% Ho3+ -doped bismuth phosphate (BiP) glasses with different (0, 5, 10 and 15 mol%) Bi content have been prepared by melt quenching method. Structural characteristics were investigated through XRD and 31P NMR spectroscopy. Optical characteristics were explored through optical absorption, photoluminescence and decay lifetime computations. Using Judd-Ofelt (J-O) theory, J-O intensity parameters Ωλ (λ = 2, 4, 6) have been calculated from the absorption spectra. Radiative properties such as radiative transition probabilities (AR), radiative lifetimes (τR) and fluorescence branching ratios (βR) for different excited states of Ho3+ ions have been examined. From luminescence spectra, stimulated emission cross-sections (σe) were evaluated for the observed two emission transitions in the green (5S2+5F4 → 5I8, 545 nm) and red (5F5 → 5I8, 658 nm) regions. Among all BiP glass matrices, Bi-5 has higher σe value (6.09 × 10−20 cm2) for the transition 5S2+5F4 → 5I8 of Ho3+ ion (green emission). Chromaticity coordinates were also calculated from the emission spectra which lie in the green region for all the bismuth contained glasses. Hence the Ho-doped BiP glasses studied in the present work are potential candidates for green emission lasers.